Last month the Croydon Guardian was the first to reveal town hall finance chiefs would cut funding for the cultural hot spot in a bid to drag the council out of a budget black hole they put at £37m.
Ted Craig, the Warehouse's artistic director and chief executive, described the council's decision as "cultural terrorism".
The Croydon Guardian understands that some at the theatre fear they are being deliberately starved of cash to smooth the way for the Gateway development.
Stanhope, one of two developers battling to land the lucrative regeneration contract, has previously promised to rebuild the theatre. But Arrowcroft, the council's preferred partner, has not.
Privately, others are also concerned that a £500,000 Warehouse trust fund held by the council could also be lost.
Mr Craig is calling on the Warehouse's supporters to unite to help win back the council grants of around £125,000 a year.
He said: "We want the support of the Croydon people on this. We've already got a big body of support and we've got to motivate the council to realise they have made the wrong decision and change their minds.
"We've had a good relationship with the council but this time they've got it wrong."
The theatre's chief executive said the decision to withdraw their funding made little financial sense.
"If the council is £37m in debt what difference will £125,000 a year make? They are cutting a huge part of Croydon's culture. We employ local actors, we are part of Croydon's night time economy and earn more than 50 per cent of our income.
"Having the grant allows us to keep our prices to a minimum, so having it withdrawn mean the possibility of increasing ticket costs. By taking away the grant the council is taking culture away from the people of Croydon."
Mr Craig also blasted the council's decision to withdraw the final quarter of this year's grant. "We are not even going to get the third quarter of this year's grant and that is the really bad part. At the very least we should have received the remainder of this year's grant.
"We've got a published programme of shows so the council should have at least honoured this year's payment - but they haven't even done that."
Labour councillor Tony Newman, leader of the opposition, has questioned the Conservative's commitment to the cultural services and agreed with Mr Craig's view that the £125,000 per year is merely a "drop in the ocean".
He said: "When Labour ran the council, they managed to support the Warehouse with a modest grant, but this hastily taken decision from the Tories will have catastrophic consequences for them.
"When the council has a budget of £443m, and this cut will only represent 0.01 per cent, with a cost to residents of less than one pence a week, this represents a savage attack on the sports and culture provision in the borough."
In response to Coun Newman's comments, leader of the council Mike Fisher said: "I think it's pretty rich for Tony Newman to lecture me on money management, we are in this problem because of the previous administration.
"Councillor Newman may see the Warehouse cut as only a small saving but it is that type of money management that got us in this position in the first place. If they had looked after our finances more responsibly then we wouldn't be in this situation."
Anyone interested in helping the campaign should call 020 8681 1257.